Increase in dopamine metabolites in murine striatum after oral exposure toinorganic but not organic form of selenium

Selenium (Se) is an essential as well as a toxic trace element. Se intoxica tion has been reported in both livestock and humans. The central nervous sy stem is sensitive to Se poisoning; exposure to Se causes blind staggers in cattle, poliomyelomalacia in pigs, and nervous system disorders in humans. Differences in neurotoxicity between inorganic and organic Se have been dem onstrated. In this study, groups of five male BALB/c mice each were adminis tered sodium selenite or selenomethionine in drinking water ad libitum at 0 , 1, 3, and 9 ppm as Se for 14 days. At the end of Se exposure, their brain s were removed and dissected into different regions. The concentration of n orepinephrine (NE), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homo vanillic acid (HVA), serotonin (5-HT), and 5-hydroxyindolacetic acid Q-HIAA ) were determined in each brain region. Food and water consumption and body weight gain were significantly decreased in the group treated with the hig hest concentration of sodium selenite. In mice administered sodium selenite at 3 and 9 ppm, DOPAC was significantly higher in the striatum than in the control group. The striatal HVA was also increased in the group treated wi th 3 ppm Se; the DA showed a similar pattern, but the increase was not stat istically significant. No alterations of NE, 5-HT, or 5-HIAA levels were de tected in any brain region of mice treated with sodium selenite. No signifi cant differences in any parameter among the groups treated with selenomethi onine were observed indicating that inorganic Se was more neurotoxic than o rganic Se via drinking water. The alterations of DA metabolites by inorgani c Se in DA-rich striatum suggested a Se-specific increased neural activity of dopaminergic pathways. Results may be useful in further elucidation of n eurotoxicity of Se and in establishing a safe level of intake for this elem ent.